// https://leetcode.cn/problems/remove-nth-node-from-end-of-list/?envType=study-plan-v2&envId=top-100-liked



/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
    ListNode* removeNthFromEnd(ListNode* head, int n) {
        ListNode* ret = new ListNode(0, head);
        ListNode* first = head;
        ListNode* second = ret;
        while(n--) {
            first = first -> next;
        }
        while(first) {
            first = first->next;
            second = second->next;
        }
        second->next = second->next->next;
        ListNode* ans = ret->next;
        delete ret;
        return ans;
    }
};